CEH describes FIN scans as stealthy scans that send packets with the FIN flag without initiating a TCP handshake. According to TCP RFC behavior, closed ports respond with RST packets while open ports ignore the probe, producing no response. This allows enumeration of port states while evading IDS systems that typically monitor SYN-based scans.

Bluesnarfing is the unauthorized access of information from a wireless device through a Bluetooth connection, often between phones, desktops, laptops, and PDAs (personal digital assistant).

Many network and system administrators don't pay enough attention to system clock accuracy and time synchronization. Computer clocks can run faster or slower over time, batteries and power sources die, or daylight-saving time changes are forgotten. Sure, there are many more pressing security issues to deal with, but not ensuring that the time on network devices is synchronized can cause problems. And these problems often only come to light after a security incident.
If you suspect a hacker is accessing your network, for example, you will want to analyze your log files to look for any suspicious activity. If your network's security devices do not have synchronized times, the timestamps' inaccuracy makes it impossible to correlate log files from different sources. Not only will you have difficulty in tracking events, but you will also find it difficult to use such evidence in court; you won't be able to illustrate a smooth progression of events as they occurred throughout your network.

Passive reconnaissance focuses on collecting information without directly touching or interacting with the target's systems. CEH materials stress that any action that sends network traffic to the target-such as scanning, probing, fingerprinting, or enumeration-creates logs and increases the risk of detection. Email headers, however, are considered an excellent source of passive intelligence because they reveal internal IP structures, routing paths, mail server hostnames, internal domain formats, and technology stacks without requiring interaction with the target environment. Since these headers are already in the possession of the ethical hacker through legitimate communication records, examining them does not generate traffic or trigger monitoring systems. SSL certificates and WHOIS data provide valuable external information, but they rarely disclose internal addressing schemes. Active scanning tools, such as Nmap, would immediately violate the requirement to avoid detection. Therefore, analyzing previously received email headers is the most effective and covert method for extracting internal network details during the reconnaissance phase.

OSINT-based reconnaissance includes using search engines to identify publicly exposed cloud assets. CEH highlights Google dorking as a passive method to reveal S3 buckets indexed in search engines through patterns such as site:s3.amazonaws.com or keyword-based queries.